This proposal requests funding to establish a DNA microarray core facility at the University of California, San Diego School of Medicine. Two instruments are requested that will provide state-of-the-art capabilities for the analysis of gene expression; the Beecher Instruments Model A9600 fully automated cDNA microarrayer and the Beecher Instruments Model R3000 scanning confocal laser reader. These instruments are based on prototypes built for the Laboratory of Cancer Genetics at the National Human Genome Research Institute (NHGRI). The microarray core facility will thus directly benefit from the continuous evolution of software and protocols developed at the NHGRI. The cDNA microarrayer and scanning confocal laser reader will enable users to assess changes in patterns of gene expression, investigate mechanisms of mRNA processing, detect expression polymorphisms and analyze genomic rearrangements. The ability to make custom cDNA arrays will enable investigators to exploit model organisms such as Dictyostelium and yeast, as well as to perform focused evaluations of specific genetic pathways at low cost. This instrumentation will revolutionize the analysis of gene expression by the participating users, provide an important resource for training graduate students and postdoctoral fellows, and serve as a focal point for interactions between molecular biologists, geneticists and computer scientists.